i 

j THE ARTIFICIAL USE OF THE 

BROWN-TAIL FUNGUS 

IN MASSACHUSETTS 









WITH PRACTICAL SUGGESTIONS FOR 

PRIVATE EXPERIMENT, AND A BRIEF 

NOTE ON A FUNGOUS DISEASE OF 

THE GYPSY CATERPILLAR 



BY A. T. SPEARE, ASSISTANT PATHOLOGIST 
HAWAIIAN SUGAR PLANTERS' ASSOCIATION 

and R. H. COLLEY, austin teaching 

FELLOW IN BOTANY, HARVARD UNIVERSITY 



UNDER THE DIRECTION OF 

F. W. RANE, STATE FORESTER 

OF MASSACHUSETTS 




BOSTON: WRIGHT & POTTER PRINTING COMPANY 
STATE PRINTERS - - 18 POST OFFICE SQUARE 

1912 



il 



: 



PLATE I. 




A winter nest with young larvae dead from the disease scattered all over the surface. 



THE ARTIFICIAL USE OF THE 

BROWN-TAIL FUNGUS 

IN MASSACHUSETTS 



WITH PRACTICAL SUGGESTIONS FOR 

PRIVATE EXPERIMENT, AND A BRIEF 

NOTE ON A FUNGOUS DISEASE OF 

THE GYPSY CATERPILLAR 



BY A. T. SPEARE, ASSISTANT PATHOLOGIST 
HAWAIIAN SUGAR PLANTERS' ASSOCIATION 

and R. H. COLLEY, austin teaching 

FELLOW IN BOTANY, HARVARD UNIVERSITY 



UNDER THE DIRECTION OF 

F. W. RANE, STATE FORESTER 
OF MASSACHUSETTS 




BOSTON: WRIGHT & POTTER PRINTING COMPANY 
STATE PRINTERS - - 18 POST OFFICE SQUARE 

1912 






SB 94 5 



OCT 30 1912 



Approved by 

The State Board of Publication. 



INTRODUCTORY. 

This report is published in order to acquaint our people with 
the beneficial results to be derived from utilizing a fungous 
disease in destroying the brown-fail' moth, which is so destruc- 
tive to our deciduous trees an<jl also so obnoxious to our people 
on account of the rash incident upon the contact of its hairs with 
the human skin. 

The report is based on a manuscript of Dr. G. P. Clinton, on 
the manuscript and notes of Mr. A. T. Speare and on personal 
observation and experiment by Mr. R. H. Colley, and was sug- 
gested by the apparent success of experiments made by Dr. Ro- 
land Thaxter of Harvard University at Kittery Point, Me., in 
the summer of 1907. 1 At this time former Superintendent 
Ivirkland of the Moth Commission became interested in the 
matter, and on the advice of Dr. Thaxter the services of Dr. 
G. P. Clinton of the New Haven Agricultural Experiment Sta- 
tion were secured, and preliminary experiments were continued 
under his supervision from May 12 to July 11, 1908. Dr. Clin- 
ton was assisted during June and July by Mr. A. T. Speare, who 
was later employed permanently by the State Forester to suc- 
ceed Dr. Clinton, and who had immediate charge of the investi- 
gation from July, 1908, until February, 1911, while during the 
past year it has been in charge of Mr. R. H. Colley. All of 
the laboratory experiments connected with this work have been 
conducted in the cryptogamic laboratories or at the Botanic 
Garden of Harvard University. 

ACKNOWLEDGMENTS. 

The State Forester and all concerned in the work wish to 
acknowledge their indebtedness to Professor Thaxter for sug- 
gestions as to experimental methods and for general direction 
and advice. Through the courtesy of Dr. G. L. Goodale and 
Mr. Cakes Ames, the directors of the Botanic Gardens, the suc- 
cessful propagation of the disease through the winter and the 

1 See Professor Hitchings's report in Maine Dept. Agri. Bur., 3, 20, 190S. 



preparation of infection material on a large scale, have been 
rendered possible. 

Thanks are also due Mr. Worthley, assistant in moth work, 
Messrs. Fiske and Burgess of the parasitic laboratory at Mel- 
rose Highlands, and to the division and local superintendents 
of the regular moth staff for their co-operation, and for cour- 
tesies rendered. 

For the work on the fungus of the gypsy caterpillar, which 
has not as yet developed so satisfactorily as that on the brown- 
tail, we are wholly indebted to Harvard University through its 
friends in financing the expedition to Japan, where the disease 
was secured. The kindly offices of Harvard University, through 
Dean Sabine and his colleagues in assisting the State Forester 
in making this work possible, are herewith heartily acknowl- 
edged. 

F. W. KANE, 

State Forester. 
Boston, March 22, 1912. 



THE ARTIFICIAL USE OF THE BROWN-TAIL FUNGUS IN 
MASSACHUSETTS, WITH PRACTICAL SUGGESTIONS 
FOR PRIVATE EXPERIMENT, AND A BRIEF NOTE 
ON A FUNGOUS DISEASE OF THE GYPSY CATER- 
PILLAR. 

SOME FUNGOUS DISEASES WHICH HAVE BEEN USED 
ARTIFICIALLY. 

The conditions governing the artificial spread of a fungous 
disease among insects vary according to the type of fungus used 
and the characters and habits of the pest to be attacked. All 
classes of insects have their fungous enemies, — some, like the 
Entomophtliorece, the species of Cordyceps and its Isaria con- 
dition, as well as other forms belonging to the Fungi Imperfecta, 
often causing serious epidemics, while others, like the Laboul- 
beniales, may be comparatively harmless. The idea of using 
fungous diseases in a practical manner to control the ravages 
of noxious insects is not a new one, and as early as the middle 
of the last century De Bary, Tulasne and others called the atten- 
tion of agriculturists and orchardists to the importance of white 
muscardine, Isaria densa Link., as a natural check on destruc- 
tive insect pests. Since the time this suggestion was originally 
made there have been numerous more or less successful attempts 
to use fungous diseases artificially, among which the following 
may be mentioned. 

Metchnikoff (1878) cultivated Metarhizium anisoplias 
(Metch.) Sorokin, the so-called green muscardine, and infected 
Anisoplia with the spores. Krassilstschik (1884) founded a 
laboratory at Smelk in order to raise green muscardine in large 
quantities, and the spores, spread on the beet fields to infect 
Cleonus punctiventris, the beet weevil, started an artificial epi- 
demic which is said to have killed from 50 to 80 per cent of 
these destructive beetles. Rorer (1910) has also used the spores 
of the same fungus, mixed with flour, in spraying sugar cane in 
Trinidad to control the froghopper, with some success. 



6 

Cordyceps melolonthce Tul. has been employed against the 
white grub, Melolontha vulgaris, in Europe, and Giard (1893) 
records an attempt to use Isaria densa against the same insect 
in France, contrasting the results obtained with those of certain 
American investigators. Buisson (1892) used Botrytis tenella 
Sacc. against the same pest. 

Sporotrichum globuliferum Speg. has been used by Snow 
(1889), Forbes (1888), Brunner (1902) and others on the 
chinch bug in this country, but although various opinions have 
been expressed as to the success of this work, the more recent 
experiments of Kelly and Parks (1911) lead them to the con- 
clusion that, although under certain conditions the fungus may 
be very destructive in nature, its artificial propagation is not 
to be recommended, an opinion in which Messrs. Billings and 
Glenn (1911) also concur. Brunner has also used it on the 
migratory locust in the Argentine Republic, and reports its 
use in the fight against the same pest in Sterling, Col. 

Sphwrostilbe coccophila Tul., Microcera sp. and Ophionec- 
tria coccicola E. and E. have been successfully employed (Rolfs, 
1907, and Fawcett, 1908) against the San Jose and purple scale 
of orange trees in Florida. During the last three or four years 
the use of Aschersonia aleyrodis Webber, Aschersonia flavo- 
citrina P. Henn and JEgerita Webberi Fawcett (Fawcett, 1908, 
Rolfs, 1908, and Berger, 1910) has been very successful in 
checking the white fly in the citrus groves of Florida, a region 
especially well adapted for such experiments, owing to the 
fact that here these fungi grow naturally out of doors more or 
less continuously throughout the year. 

Of the Entomophthorece, although the group contains some 
of the most destructive forms attacking economically important 
insects, the brown -tail fungus appears to be the only form which 
has been used artificially. That more of these forms have not 
been used is probably due to the fact that their cultivation and 
propagation is usually attended with the greatest difficulty. 

THE BROWN-TAIL FUNGUS. 

The fungus which causes the disease of the brown-tail cater- 
pillar is a microscopic plant known technically as Entom-o- 
phthora Aulicce Reich, which has been long known in Europe 



PLATE II. 




a be 

Fig. 1. 
Fig. 1. — a, gypsy moth larva from Japan killed by an Entomophthora disease; 1>, 
tent caterpillar, and c, three brown-tail larva- killed by 'Entomophtlwra Aulicw. T 
latter were kept in a dark chamber to develop an external growth of the fungus. 




Fig. 2. 
FIG. 2. —This photograph gives some idea of the number of spores discharged. The 
branch, crowded with dead and dying caterpillars, was laid on a sheet of glass in a 
still room, and the white color is entirely due to the thousands of spores which fell 
on the glass during the night. 



and was first reported from this country by Dr. Thaxter in 
1888. It has not only produced natural epidemics among the 
brown-tails since they were first introduced, but it attacks vari- 
ous other native species of insects, which are enumerated below. 
It is closely allied to EntomopMhora muscco Cohn, a fungus 
that attacks the common house fly, which may often be seen 
dead on a window pane or mirror, where it becomes surrounded 
by a white halo or whitish patch, due to the large number of 




Fig. 1. — Diagram to illustrate the development and 'discharge of spores. 
At the tip of the club-shaped conidiophore a a rounded bud 6 develops 
into the pear-shaped spore c. This spore is torn away at the collar d 
when mature by internal pressure, and shot off from the conidiophore 
f, as indicated by the arrow at e. Spores produced and discharged in 
this manner are called conidia. At g is shown a germinating spore 
with its young germ tube. 

spores discharged on the glass. (Plate II., Fig. 2.) These 
spores, called conidia, which are the fruit of the fungus, and 
correspond in function to the seeds of higher plants, are ovoid 
to pear-shaped (Plate VII., Figs. 1-4), with a papillate base, 
and measure 25 to 35 by 28 to 40 thousandths of a millimeter. 
If a spore comes in contact with a healthy caterpillar under 
favorable conditions of moisture, germination takes place imme- 
diately; that is, the spore sends out a thread-like germ tube. 
(Fig. 1, g; Plate VII., Figs. 5-7; Plate VIII., Fig. 32.) 
This germ tube pierces the integument and continues to grow 



within the body of its victim for about five days after infection. 
Germination may also take place on any moist surface, but in 
such cases growth is usually very limited, and may result in 
the production of secondary conidia (Plate VII., Fig. 8) 
exactly similar to the primary conidia, which may be dis- 
charged when mature and have the same power of infecting a 
healthy larva. The conidia retain their power of germination 
for about seventy-four hours after their discharge. In nature 
the caterpillar is not visibly affected by the presence of the 
fungus in its body until the afternoon of the fifth or sixth day, 
when, after a brief period of nervous activity, its movements 
become sluggish or cease altogether. By this time the branches 
from the original germ tube have become broken up into irreg- 
ular chunky " hyphal bodies," which more or less completely 
fill the body cavity. Just before death, which usually comes 
toward evening, the caterpillar is almost always impelled to 
climb to the highest point on the leaf or twig on which it has 
been resting; the forelegs then lose their power, and the fore 
part of the body droops backward or to one side in a position so 
characteristic as to be easily recognized. (Plate VI.) As soon 
as the caterpillar is dead, or even just before death, the hyphal 
bodies within it send out stout germ tubes. (Plate VIII., Figs. 
28-31.) The ultimate branches of these germ tubes break 
through the integument in pustules (Plate VIII. , Fig. 26), 
which may eventually cover the whole body with a creamy white 
mass of fungous growth, especially if the atmosphere is moist. 
At the tip of each of the club-shaped branches, called conidio- 
phores (Fig. 1, a, b; Plate VII., Fig. 10), a rounded bud 
develops into the pear-shaped spore (Fig. 1, c, e), which is 
shot off with considerable force when mature by a mechanism 
specially developed for this purpose. Air currents may carry 
the spores for miles, or if they fall on the backs of other cater- 
pillars the movement of the latter may perhaps further aid in 
their distribution, especially where the caterpillars are closely 
congregated. The number of spores which may be discharged 
from a single diseased larva is very large, probably reaching 
hundreds of thousands in the case of a full-grown caterpillar, 
and every spore has the power to infect another caterpillar, 
provided that it strikes in a favorable position for penetration 



under favorable conditions of moisture. It is interesting to note 
that nature has provided for the wider dissemination of these 
spores by impelling the dying caterpillar, as already mentioned, 
to climb upward, thereby placing its body in a more elevated 
position, from which the falling spores will be distributed over 
a large area. In the field the dead caterpillars are found most 
often on the shady under side of the limbs, near the crotches 
of the branches, but one may find them with little trouble on 
any part of the tree or on adjacent walls and fences. (Plate 
III.) 

Resting Spores. 
Besides the type of " air spores " or " conidia " just de- 
scribed, the fungus produces another type, formed internally, 
known as " resting spores," which are extremely resistant to 
changes of heat and cold, and which, although their germina- 
tion has not been observed, undoubtedly serve to tide the fungus 
over winter. They are commonly formed by the rolling to- 
gether of the contents of large, irregular, fungal elements 
(Plate VII., Figs. 12-18) into spherical bodies, which later 
become enclosed in very thick walls. Spores of this type are 
comparatively rare, and the conditions which lead to their form- 
ation, whether they be due to internal causes, or to the effect of 
weather, or other external influences, are not clearly under- 
stood. 

Encysted Hyphal Bodies. 

In the fall the hyphal bodies may themselves also become 
surrounded with heavy walls, which on germination split and 
let out the contents in the form of stout germ tubes. (Plate 
VIII., Figs. 22, 23.) The latter branch freely, and give rise 
eventually to pustules (Plate VIII., Fig. 25), as in the case 
of the ordinary hyphal bodies. These encysted hyphal bodies 
are also instrumental in wintering over the fungus. 

General Conditions governing the Artificial Spread of the Fungous 
Disease of the Brown-tail Moth Caterpillar. 

In the case of the brown-tail caterpillar there are two periods 
in its life history when the Entomophthora under consideration 
may be effectively used, namely, in the spring and early sum- 



10 

mer, when the larvae have left their nests to feed on the young 
leaves, and in the autumn for several weeks before the webs 
of the new broods are closed for the winter. During both of 
these periods the rapid spread of the disease is largely depend- 
ent on weather conditions, and when these conditions — warm 
nights and damp atmosphere — favor the growth of the fungus, 
artificial distribution yields truly satisfactory results, and may 
bring about enormous and widespread destruction ; but it should 
be understood clearly that, even under these conditions, al- 
though the disease is evidently very important as a powerful 
check, it cannot be regarded as a " cure-all." In the spring, 
when the caterpillars are scattered all over the trees, it is com- 
paratively easy to place the infected larvae in among them, but 
in the autumn, when they are localized, feeding in the imme- 
diate vicinity of the nest, it is necessary to infect individual 
webs. Experience seems to point to the autumn, however, as 
the more advantageous time to start the artificial epidemic. 

Early Reports of the Disease among Brown-tails. 

Mention has been made in previous State reports of the 
occurrence of the disease in spring and fall epidemics. The 
dead larvae on the outside of the webs (Plate I.) were first 
noticed during the early winter months * of 1902 and 1903, and 
the frosty appearance of the nests, due to hundreds of thousands 
of discharged spores, led to the popular belief that the young 
caterpillars had been lured out of the webs by the warm mid- 
day sun and had been frozen to death before they could return. 
The susceptibility of the brown-tail to this disease was first 
noticed by Dr. Thaxter in Maine, just after the caterpillars 
made their initial appearance there. He had made a series of 
experiments in artificial infection previous to the experiments 
at Kittery Point, Me., in 1907, which were reported by Pro- 
fessor Hitchings, and the apparent success of which led to the 
engagement of Dr. Clinton to carry on a preliminary investi- 
gation in Massachusetts. 

1 See Fernald and Kirkland's Report of Brown-tail Moth Commission, 1903. 



11 



Preliminary Experiments of 1908. 

Dr. Clinton concluded from his preliminary experiments in 
the spring of 1908 that the use of the disease as a check would 
be of practical value if (1) the fungus were planted in terri- 
tory where the natural disease was not in evidence, and (2) if 
the plantings were made in the field before the natural disease 
could develop under ordinary weather conditions, thereby giv- 
ing the introduced disease an opportunity to develop more gen- 
erations, and consequently infect more larva? than the later- 
starting natural epidemic. He was hampered in his investi- 
gation by the fact that he was unable to begin operations until 
the season was well advanced, and the time available was so 
short that he was unable to make extensive experiments. His 
results, however, again demonstrated that the propagation of 
the disease in the field could be successfully accomplished. 

Autumn of 1908. 

Dr. Clinton being unable to continue the work after July 
of this year, it was taken in charge by Mr. Speare, and the first 
fall infection was made in the autumn of 1908, when about 
500 diseased caterpillars were distributed over a limited area 
on low shrubbery at North Andover, Mass. As nearly as could 
be estimated about 35 per cent, of the young larva? on the 
hillside where the planting had been made died as a result of 
this artificially induced epidemic. 

Cultivating the Fungus through the Winter of 1908-09. 

The Entomophthora from the fall infection was cultivated 
and kept alive through the winter months so that the spring 
planting could be made as early as possible, without the delay 
incident to spring collection and forcing of the disease. In 
order to accomplish this, webs were cut open and placed on a 
layer of filter paper over damp moss in ordinary culture dishes. 
A glass cover kept the atmosphere in the dishes moist and 
favorable to the growth of the fungus. Infected larva? were 
placed in the cut nests, and in this manner the disease was 
transmitted to the healthy larva 3 , and the fungus kept alive 
through successive generations. Some practice was necessary 



12 

before the optimum moisture conditions were determined, but 
the chief difficulty encountered was the hostile action of other 
fungi, which grew very rapidly under culture-dish conditions. 
The worst enemy, Sporotrichum globuliferum Speg., sometimes 
threatened to choke out the Entomophthora entirely. 

Spring of 1909. 

The fungus having been propagated through the winter of 
1908-09 at the Botanic Garden, about the first of March two 
bushels of webs were brought from cold storage and placed in 
two boxes, which, for the sake of convenience, will be called 
the " disease box " and the " rearing box." Both boxes were 
of the same type, their dimensions being 11 by 27 by 27 inches, 
and by leaving the bottoms open the contents were directly in 
contact with the moist earth. A two-inch rim of ordinary com- 
mercial tanglefoot served to keep the caterpillars confined. 
Dead and dying larvse from the winter culture dishes were 
turned into the disease box, together with fresh webs contain- 
ing healthy caterpillars, for the purpose of starting a general 
infection as soon as the latter emerged. In order to favor the 
spread of this infection as much as possible the atmosphere was 
kept moist by covering the box with a damp mat. Without 
attempting to force the growth of the larvae in either box, they 
were fed just enough to keep them alive, so that the disease 
might be carried along through successive generations on a 
little larger scale than was possible with the culture dishes. 

About April 1 larvre from four bushels of cold-storage webs 
were placed in five rearing boxes, and the intention was to feed 
them to the limit of their capacity, so that they would be large 
enough for infection and distribution by the 25th of the month. 
Owing, however, to the nature of the only food which was avail- 
able, the rearing of the caterpillars was attended with the great- 
est difficulty, as it was almost impossible to make them feed. 
Willow twigs forced under glass were not acceptable ; lettuce 
worked fairly well but was expensive, and the larvse did not 
thrive on it, so that little or no active growth occurred until a 
supply of fresh food became available out of doors as the season 
advanced. 



13 



Feeding Methods. 
The larvae 'were fed by two methods: (a) by placing leafy 
twigs in jars sunken in the earth, or (b) by throwing small 
quantities of stripped leaves directly on the clean earth. In the 
first method the leaves remained fresh for some time, but in 
handling the wet twigs, when changing the food or the water, 
the boxes often became too damp and favorable to the growth 
of the fungus, which, when once it gained a foothold, threatened 
to kill off the entire supply of caterpillars. The second method 
has proved to be the better for general use, because the supply 
of food can be easily regulated by throwing in just enough 
leaves to keep the caterpillars eating all the time. The boxes 
were kept clean and sanitary by removing the dried and half- 
eaten leaves as soon as the larvae crawled on fresh ones. 

General Methods of Infection. 

All investigators on fungous diseases of insects have experi- 
enced more or less trouble in transmitting the disease to healthy 
larva? in the laboratory. In most cases it seems very difficult to 
imitate exactly the conditions under which the infection nat- 
urally occurs. What is true of other fungous diseases is in 
general true of the brown-tail disease, and it often happened 
that the fungus would get a start in the rearing boxes, where it 
was not wanted, and attack the larvse with the virulence of an 
epidemic, while in the disease boxes, where the conditions were 
supposed to be at an optimum for its growth, it appeared only 
in scattered spots. The three methods used for general infec- 
tion may be outlined as follows : — 

(a) Infection by the " Crate Method/' — A crate 5 V> by 30 
by 30 inches, with a mosquito netting bottom, was fitted tightly 
over a second crate of similar dimensions, in which the healthy 
larva? were placed. Caterpillars dying from the disease or those 
already dead and ready to discharge spores were placed at 
short intervals on the netting bottom of the upper box, so that 
the spores from their bodies would drop through the meshes 
of the netting upon the healthy larva? below. 

(b) Infection by the "Spray Method." — Dead caterpil- 



14 

lars were placed in an atomizer bottle so that all of the spores 
discharged would be caught on the glass. After spore dis- 
charge had ceased, and the bodies of the caterpillars had been 
removed, the bottle was filled with water, the spores were dis- 
lodged from the sides and bottom with a soft camel's-hair brush, 
and the " spore water " was then sprayed over healthy cater- 
pillars in an ordinary rearing box. 

(c) Infection by the "Natural Method." — Infected larvae 
were mixed with healthy ones all over the twigs and leaves in 
a rearing box. Following their natural instinct to climb, the 
diseased caterpillars placed their bodies in such elevated posi- 
tions as the tips of the twigs and sides of the box just under 
the rim of tanglefoot, so that the spore discharge was directed 
against the bodies of the healthy caterpillars and in every direc- 
tion over the leaves. 

By taking lots of 100 at random from these boxes, after they 
had been exposed to the spray or spore discharge for three or 
four days, placing them in small trays and counting the number 
which died from the disease within nine days, it was found that 
the maximum infection was hardly more than 40 per cent. 1 
The last method appeared to be the most favorable, and was 
adopted for the infection of all of the material sent into the 
field. 

General Methods of Distribution. 

After trying several schemes for distributing the infected 
larvse it was concluded that the method first used by Dr. Clin- 
ton could not be bettered for general use, because of its sim- 
plicity and comparatively low cost. The method in brief is as 
follows : From 20 to 30 caterpillars which had been exposed 
to the spore discharge were placed in a quarter-pound paper 
bag, the neck of which was wound tightly with a 10-inch strand 
of JSTo. 26 iron wire. The bag was then hung in the tree as 
near the web as possible, or near the masses of feeding cater- 
pillars, and its side ripped open to allow the infected larvae 
to escape. In addition to this bag method, wherever it was 
possible the sick caterpillars were placed directly in the feeding 
masses, thus practically insuring an infection. 

1 This maximum was increased by a combination of methods to 75 per cent, in 1911. 



PLATE III. 




Fig. 1. 
Fig. 1. — Showing dead larva? on the top of an old stone wall at South Billerica. 




Fig. 2. 

Fig. 2. — A \irw of a single stone of the above wall. All of the larva: shown are dead 

from the Entomo2)hthora disease. 



15 

The plantings x of the spring of 1909 were made by the two 
methods just described. In nearly every case the larvae 
crawled out of the bag in a few minutes, but in the first two 
plantings made in late April, the cold rendered their move- 
ments so sluggish that they died before they could escape. The 
last three plantings were made' so late in the season that they 
could not have been very effective. The season's work proved 
that artificial spread before May 1 is useless, because the irreg- 
ular cold weather of late April inhibits the growth of the 
fungus, and that it is extremely difficult to estimate the effec- 
tiveness of plantings made after May 25 on account of the 
prevalence in the field at this season of spontaneous epidemics. 
In the territories of Rowley and West Newbury, where the 
disease worked very successfully, the final mortalities among 
the prep is pa? and pupa? ranged from 80 to 90 per cent., and in 
localized plots of intense infection it was impossible to find a 
single live individual. 

On May 14 the number of caterpillars dead from the disease 
on the territory at North Andover, planted the previous fall, 
was estimated at 50 per cent., and on May 28 at 95 per cent. 
The epidemic had apparently spread about equally well in all 
directions. Inspection of the estate of Mr. William Brewster at 
Concord, where a natural infection had occurred in the fall, 
showed that the caterpillars were practically annihilated by the 
24th of May. It seemed probable that the epidemic in the 
North Andover territory had been started by the diseased cater- 
pillars planted there in the fall of 1908, since there was no 
indication of the fungus in that locality previous to their in- 
troduction, and in both cases the early appearance of the dis- 
ease in the spring, and the intense destruction wrought by it, 
seemed to point to the conclusion that the fungus had wintered 
over in the nests, and begun its attack as soon as the young 
larva? emerged. 

Autumn of 1909. 

In the autumn of 1909, the supply of webs in cold storage 
being insufficient, only three plantings were made, two of which 
were effective in killing off 20 to 30 per cent, of the larva?, thus 

1 See page 26 for list of localities planted. 



16 

confirming the results of the preceding fall; the other was 
spoiled for observation because the infected webs were cut 
from the trees and burned by the owner of the property. 

Spring of 1910. 

The fungus was carried over the winter of 1909-10 in cul- 
ture dishes by the method already outlined, and a general infec- 
tion started in the disease boxes in the usual manner. A disas- 
trous epidemic of Sporotrichum globuliferum Speg., which 
killed off a large number of the larvse and threatened to choke 
out the Entomophthora altogether, was controlled only with the 
greatest difficulty. In spite of this hindrance, however, a suffi- 
cient quantity of infected material was ready for planting on 
the 1st of May. The diseased caterpillars were distributed over 
a solid block of territory about twelve square miles in extent, 
running along the railroad track from Ipswich to within one 
mile of the New Hampshire line, and also in six scattered 
plantings on private estates. Weather conditions were favor- 
able, and regular inspection at intervals during late May and 
early June revealed a mortality estimated at about 35 per cent., 
with the disease universally distributed through the planted 
areas. The virulence of the epidemic gradually increased until 
the larvse began to spin up, about the middle of June, when 
the per cent, of those visibly affected rose so high that only 80 
out of 1,000 pupae and prepupae collected from all over the 
planted territory matured moths. 

It might be stated here that the word per cent, as used above 
should not be taken in its literal sense, as it is impossible to 
arrive at an absolutely correct determination of the work of the 
fungus at any given moment. The reasons are obvious. Only 
those caterpillars visibly affected with the disease at the time 
of inspection can be used in the calculation, which means that all 
larvse which have died and dropped from the trees, as well as 
those infected but not yet dead, must be inevitably overlooked. 
Moreover, at the time of inspection the disease may be at a 
very low ebb, due to adverse weather conditions or some other 
cause, and the inspector will get the impression that the fungus 
is not working at all. Territories in which the disease ap- 



17 

peared to be working to perfection in May often exhibit only 
scattering evidence of the destruction wrought when inspected 
in June, and in other territories the June death rate may be 
the highest of the season. Since the conditions in the field are 
so variable, careful inspections and estimates must be made at 
intervals throughout the entire season in order to arrive at 
even an approximate estimation of the total work that the 
fungus has done. 

Autumn of 1910. 
Seventy bushels of webs were brought from cold-storage on 
the 25th of July to furnish the larvse for the fall infection of 
this year. The caterpillars were placed in long rearing boxes 
out of doors under favorable conditions for their growth, but 
an attack of the disease, which started from one box in which 
there must have been a few infected webs, and spread rapidly 
to all of the others, killed off 90 to 95 per cent, before the 
20th of August. The few that survived were evenly distributed 
in five disease boxes, and with them were mixed healthy larva? 
from the webs in the field. Although this meager supply of 
diseased material was unsatisfactory, about forty plantings 
were made, with the co-operation of the State agents and super- 
intendents, on low shrubbery in eastern Massachusetts. A new 
method of sending the caterpillars to the field, in mailing cases, 
was tried in connection with these plantings, and proved to be 
satisfactory, except in those instances where the cases were 
delayed in the mails until the larva? were dead when they 
arrived at their destination. In making the plantings all the 
nests that could be conveniently reached were ripped open, so 
that a few of the infected caterpillars could be inserted directly 
among the healthy occupants. The bag method was also used 
successfully. Where the contour of the country permitted, the 
plantings were made at 50-foot intervals, and the whole planted 
territory divided into plots of convenient size for careful ob- 
servation. A count of all of the nests in a selected plot was 
recorded at the time of planting, so that the spread of the dis- 
ease might be checked up at each inspection. The reports of 
the inspectors showed that the disease became evident after 
ten days in every plot, and that the number of dead larvse on 



18 

the outside of the nests increased very rapidly, first in the 
immediate vicinity of the infected web, and then in scattered 
spots all over the territory. The following typical report from 
two inspections of a planting made August 13 at Clinton gives 
some idea of the rapid death rate. One bag, containing 15 to 
20 diseased caterpillars, was hung in the middle of each plot, 
and the plots so chosen that the bags were about 50 feet apart. 



Plots. 


Total Number 

of 
Webs ia Plot. 


Webs 

Infected 

September 10. 


Dead Larvae 
September 10. 


Webs 

Infected 

September 15. 


Dead Larvae 
September 15. 


I 

II 

III., . 
IV., . 


12 
10 
23 
20 


4 
3 
6 
6 


67 
46 
149 

78 


10 
9 
15 
13 


231 
340 
410 
177 



The area of each plot was between 400 to 500 square feet. The 
same results were reported from the other plantings, which 
were practically all successful, resulting in the infection of 35. 
to 50 per cent, of the webs in the planted areas. 



Spring of 1911. ' 
Following the same general methods in rearing, infecting 
and distributing the caterpillars used in previous experiments, 
the work of the spring of 1911 was continued on a still larger 
scale. The only change in the rearing and disease boxes was 
the use of heavy wire screening with a quarter-inch mesh on 
the bottoms, to retain a thin layer of earth and prevent the 
escape of the larvae whenever the boxes had to be moved. The 
late spring, and consequent late opening of the foliage, made 
the work of early rearing very difficult, and it was necessary to 
draw on a supply of raspberry leaves, grown in the greenhouse 
and intended for use in raising gypsy larva?, until the willow 
and cherry trees came out. Beside the extensive plantings 
made by two men employed especially for the purpose during 
the month of May, a general distribution of infected caterpil- 
lars was made possible with the help of the State agents. Ship- 

1 Mr. Colley took full charge of the work in February, 1911. 



PLATE IV. 




Fig. 1. 

Fig. 1. — Long rearing boxes under the trees at the Botanic Garden, used to force the 

larv:c. for the infection experiments of the fall of 1910. 




Fig. 2. 
FIG. 2. — Rearing boxes protected by cotton drilling to prevent the spread of an epi- 
demic of the disease in the fall of 1910. It was thought that the cotton cloth would 
stop spores from being blown in from the infected boxes. 



19 

ments were made also to interested persons all over the State 
for private experiment, as long as the material lasted. 

The extreme dryness of the month of May hindered the 
growth of the fungus to a very large extent, so that the final 
results were not as good as those of the preceding spring, but 
toward the end of the season there was a general infection all 
over the planted territory. In and around Ayer the number 
of caterpillars visibly affected with the disease on the 27th of 
June was estimated at 60 to 70 per cent., and the trees in 
which the fungus had been planted were not nearly so badly 
stripped as those in which the caterpillars had been unmo- 
lested. In contrast to this condition a badly infested scrub 
growth of oak and cherry in Roberts, where no fungus had 
been planted, was completely defoliated, and the natural dis- 
ease, though evident on one or two bushes, was not present in 
epidemic form. 

Early inspection of the plantings made in the autumn of 
1910 showed that the infection was general, but was not spread- 
ing far from the planted areas, except in one or two instances. 
In spite of this fact the defoliation in these areas was notice- 
ably less than in areas where no fungus had been distributed. 
As in the spring of 1910, the death rate after the 15th of June 
increased very rapidly, and in Georgetown, where an excellent 
infection was started the previous September, the caterpillars 
in the planted territories were almost completely annihilated. 
The territory between Ipswich and Rowley, which is damp 
nearly all the time, on account of the proximity of the ocean 
and salt marshes, was found to be practically cleared of brown- 
tails by the disease. 

Autumn of 1911. 

In preparation for the fall infection the larva? were brought 
from cold storage on the 15th of August, three weeks later 
than in previous seasons, and fed wholly on cherry. Fortu- 
nately, the disastrous results which attended our efforts to force 
the caterpillars in July and August, 1910, were not repeated, 
so that ten bushels of webs furnished an abundant supply of 
larva? about one-half inch long by the 1st of September. It 
was found advisable to cover the bottoms of the rearing boxes 



20 



with a thin layer of coarse gravel, which was a great aid in 
keeping the boxes clean. Two disease boxes had been run all 
summer, and from them infection was started in seven others. 
The latter were all arranged as shown in Fig. 2, and by a com- 
bination of the " natural method " and the " spray method " 
a comparatively high per cent, of infection was obtained. The 
following table shows the results obtained in five test experi- 
ments. In each case the caterpillars were picked at random 
from the disease boxes and packed in mailing cases for several 
hours, as if they were to be shipped to agents in the field, to 
imitate the normal conditions of distribution, before being 
placed in the observation trays. 



Trays. 


Number of 

Larvae placed in 

Tray. 


Number of 

Larvae dying within 

Nine Days. 


Approximate 
Per Cent. 




180 


97 


53 




253 


204 


80 




219 


183 


83 




144 


109 


75 




129 


97 


75 



Planting was commenced on the 1st of September and ended 
on the 12th, during which time approximately 100,000 cater- 
pillars were distributed, a great increase over the number dis- 
tributed in the fall of 1910. The caterpillars, packed in mail- 
ing cases as before, were delivered by automobile, a method 
which assured their reaching the agents in good condition, be- 
cause by its use unnecessary delay in transit was avoided. 
With one or two exceptions all of the infected caterpillars were 
planted directly in the nests. 

About the middle of October an inspection of all the nests on 
plotted areas in plantings in Waltham, Stow, Marlborough and 
Hudson showed a general infection, about half of the nests 
examined being diseased. 1 In all of this autumn's work only 
three cases of naturally infected webs were observed, a fact 
which led to the conclusion that the epidemic in these areas 

1 The number diseased was 763 out of 1,623, by actual count. 



21 

was due to the infection started by the introduced caterpillars. 
There is every indication that, with favorable weather condi- 
tions, the work of the fungus will be evidenced in the spring of 
1912 by a more or less complete annihilation of the brown-tails 
in and around the territories where the plantings were made 
this last autumn. 

In summing up the results of the investigations covering the 
four seasons 1908-11, it may be said that it has been found 
possible to propagate the disease in the laboratory, and to infect 
caterpillars in the field successfully, both in the spring and in 
the fall. Under favorable weather conditions the artificially 
induced spring epidemics have resulted in many cases in the 
practically complete destruction of the larvse in the planted 
areas. In the fall epidemics the number of nests infected at 
the end of the season has ranged from 30 to 50 per cent., and 
these nesfs have apparently formed the starting point of early 
spring infections. The fall plantings have, therefore, a two- 
fold efficiency, in that they not only result in the destruction 
of one-third to one-half of the caterpillars in the autumn, while 
they are small and comparatively harmless, but also, by es- 
tablishing the disease in the nests, enable an epidemic to get 
started much earlier in the spring than any natural infection 
could develop under ordinary weather conditions. The last 
three or four years have not been particularly favorable for 
natural epidemics or for furthering the spread of the intro- 
duced disease, and it seems reasonable to suppose that the fun- 
gus would have been far more effective if the weather, espe- 
cially during the spring months, had been warmer, with a 
larger rainfall. It has, of course, been impossible to plant all 
of the infested territory with diseased caterpillars, and in many 
cases areas cleared of brown-tails by the fungus in the spring 
have been invaded by moths from uninfected localities, with 
the result that they were infested as badly as ever in August. 
This condition of affairs is unavoidable, since we are dealing 
with a moth that may fly, or be blown, for some distance, and 
it is therefore impossible to guarantee that the fungus will 
clear any territory of moths so that it will remain free for 
any length of time. The presence of the disease does not ren- 



22 

der a territory immune to future immigrations, but it certainly 
will reduce the amount of damage that the invading moths 
may do. The determination of the distance to which the dis- 
ease may spread is extremely difficult. Undoubtedly the spores 
are often blown for miles, and in such cases the epidemic 
might jump from one territory to another widely separated 
from it, but there would be no means of telling just where the 
spore or spores which started the second epidemic came from. 
As can be seen from the table on page 18, one bag of 20 to 30 
diseased caterpillars is sufficient to infect an area of approxi- 
mately 625 square feet; any further spread of the disease would 
be variable, and dependent upon weather conditions. 

Webs in Cold Storage. 

Before giving general directions for private experiment it 
seems advisable to mention the advantages of having a supply 
of webs in a cold-storage warehouse, or packed in a dry box in 
an icehouse where the temperature does not go over 35 degrees, 
to furnish the proper amount of material at short notice for 
spring or fall work. It is difficult to collect larvae just when 
they are needed in the spring, for the caterpillars have usually 
started to feed, and it is impossible to collect them in the sum- 
mer in time for the fall work, for they do not emerge from 
their eggs until the middle of August. Care should be taken 
that such webs as are selected for this cold-storage supply are 
not infected with the disease at the time of collection, for if 
they are it will become epidemic when the nests are brought 
out into the warmer air, and completely destroy the larvae in 
the rearing boxes. 

Directions for Private Experiment. 

With such a supply of webs to draw from, persons wishing to 
make private experiments might proceed something as fol- 
lows : — 

Two boxes should be constructed after the manner shown in 
Fig. 2, and set in two frames (Plate V., Fig. 2) some distance 
apart, one for rearing the caterpillars and one for forcing the 
disease. The bottoms of both boxes should be covered with a 



PLATE V. 




Fig. 1. 
FIG. 1. — Showing the proper method of 
hanging the bag containing the infected 
caterpillars close to the nest. 




Fig. 2. 
Fici. ■!. — A cheap but efficient frame and disease box for private experiment. 



23 



thin layer of gravel. About April 1, 200 stored or freshly 
cut webs should be placed in each box, and in addition to this 
number the box chosen for the disease box should also receive 
two or three dozen infected webs from some locality where the 
disease is known to be present. 




Fig. 2. — Diagrammatic view of the interior of a rearing or disease box. Forked sticks bbb 
driven into the ground support crosspieces cc, on which leafy twigs may be hung. Other 
leaves should be scattered on the ground beneath the crosspieces. Infected caterpillars will 
usually crawl up the forked sticks and along these crosspieces, so that the spores from their 
bodies will fall on the healthy larvae feeding below. A two-inch rim of tanglefoot in the 
position indicated by aa will keep the caterpillars confined. 



In the matter of food, sanitation, heat and shade experience 
is the only reliable guide, but in general, young buds, stripped 
from oak or cherry trees, make the best material for early feed- 
ing; the boxes, especially the rearing box, should be kept as 
clean as possible, and the shade should be arranged so that the 
temperature does not go much over 80 degrees. The disease 
box should be kept dark and moist most of the time by covering 
with a damp mat, but here again the rule is not without excep- 



24 

tion. The rim of tanglefoot, indicated in Fig. 2, should be 
frequently combed. 

After about ten days, by which time the disease should have 
made its appearance, the disease box should receive constant 
attention. Each night and morning the dead and dying cater- 
pillars should be evenly distributed among the other larva? in 
the box, in order to make the infection as general as possible. 
The " spray method " outlined on page 13 should be used in 
conjunction with this " natural method." Furthermore, it is 
particularly important, in the attempt to hasten the general 
infection, that the number of, larva? in the disease box should 
be kept nearly constant, by transferring healthy caterpillars 
from the rearing box to replace those killed by the disease. 
Broad-pointed forceps should be used in handling the cater- 
pillars. 

Planting should be commenced about the first of May, and 
can be continued to advantage until the first of June. Twenty 
to 30 of the caterpillars which have been exposed to the spore 
discharge in the disease box should be placed in a quarter- 
pound paper bag, the neck of which should then be tightly 
wired with a convenient strand of No. 26 iron wire, or other 
suitable material. The bag, when it has been hung as near as 
possible to the masses of feeding larva? or to the nests (Plate 
V.. Fig. 1), should be ripped open to allow the escape of the 
infected caterpillars. 

For successful autumn planting a supply of cold-storage webs 
is absolutely necessary, because the fungus must be kept alive 
through successive generations during the summer months in 
the disease box, and to do this one must have a few webs on 
hand all the time. Moreover, as stated before, the larva? in 
the field are not large enough for convenient handling in the 
fall experiments. The rules given for spring rearing and in- 
fection hold in general for the autumn work, except that it is 
not necessary to keep the boxes under glass. Autumn planting 
should be direct, that is, infected caterpillars should be placed 
directly into nests conveniently reached, a method which insures 
an infection and which is simpler than the bag method. Pliable 
branches may be pulled down with a hooked pole. Where there 
are a number of nests on a small bush the central nest may be 



25 

directly inoculated and the surrounding nests tied up to it with 
a piece of heavy cord, which may be cut at the first inspection, 
after the infection has spread. Another method, devised by 
Dr. Thaxter, is as follows : cut, infect and bind together half a 
dozen or more nests. To one end of a string of convenient 
length attach a small stone, throw the stone over the infested 
tree and pull the bunch of webs attached to the other end of the 
string up into the topmost branches, where the nests are usually 
crowded and the infection will do most good. All of these sug- 
gestions can be varied to suit conditions of moisture, contour 
and shrubbery on the territory which is to be planted. Where 
it is convenient the nests which have been cut from fruit trees 
may be piled in an open field or in swampy pasture land and 
the infection started in the pile. Such a method will result 
in the practically complete destruction of the caterpillars, will 
allow the escape of insect parasites which would be killed by 
burning, and will establish the starting point for an epidemic 
which should spread to the surrounding bushes and trees. It 
has been found advantageous in some cases to burlap the trees 
in which the fungus has been planted, especially in the spring, 
as the caterpillars, in crowding together under the burlap, 
easily transmit the disease to one another. 

Conclusions. 

The artificial propagation and use of the brown-tail fungus 
has been clearly shown to be an effective means of destroying 
the caterpillars of this insect in great numbers and over con- 
siderable areas. 

Although the success of this artificial use is variable, owing 
to the fact that the degree of warmth and moisture most favor- 
able for the growth of the fungus, and dependent on weather 
conditions, cannot be controlled, the introduced disease can in 
general be depended on to kill from 60 to 100 per cent, of the 
caterpillars in the planted areas. 

Plantings of the infected caterpillars should be made prefer- 
ably in localities where the natural disease is not known to be 
present, in the spring from May 1 to June 1, and in the autumn 
from August 25 to September 10. 

The fungus usually lives over winter from the autumn infec- 



26 

tion, and does effective work, as is evidenced by the early- 
appearance of the disease and the reduction of the spring defo- 
liation in localities where it was introduced the preceding fall, 
and for this reason fall infection is doubly effective. 

Artificial distribution is most easily accomplished in sprout 
woodlands and pastures where the ordinary methods of control, 
such as spraying and cutting, are not employed, and where 
the nests are more readily accessible. 

List of Localities where the Fungus has been planted. 

Spring, 1903. — Concord, Gerrish Island, Me., South Billeriea, State 
Line, Waltham. 

Fall, 1908. — North Andover. 

Spring, 1909. — Ballardvale, Chelmsford, Concord, Lowell Junction, 
Newburyport, North Andover, North Wilmington, Rowley, Salis- 
bury, West Newbury, Woburn. 

Fall, 1909. — Mishawum, North Wilmington, Newbury. 

Spring, 1910. — Territory along railroad track from Ipswich to New 
Hampshire line. Scattered plantings on six private estates. 

Fall, 1910. — Amesbury, Andover, Billeriea, Bolton, Boston, Boxf ord, 
Clinton, Cohasset, Dracut, Georgetown, Groveland, Fitchburg, 
Framingham, Harvard, Leominster, Lunenburg, Medfield, Methuen, 
Newbury, North Andover, Reading, Rowley, Scituate, Shirley, 
Tewksbury, West Newbury, Worcester. 

Spring, 1911. — Intensive planting in and around Ayer. Dunstable, 
Groton, Leominster, Lunenburg, Pepperell, Shirley, Stony Brook, 
Westford, Whalom. 

Fall, 1911. — Amesbury, Arlington, Ashland, Bedford, Belmont, Berlin, 
Boxford, Burlington, Carlisle, Concord, Danvers, Dedham, Dover, 
Fayville Dam, Framingham, Georgetown, Groveland, Hamilton, 
Hopkinton, Hudson, Ipswich, Lakeside, Lexington, Lincoln, Lynn, 
Marlborough, Maiden, Melrose, Merrimac, Needham, Northborough, 
North Reading, Newbury, Roberts, Salisbury, Saugus, South Acton, 
Southborough, Stoneham, Swampscott, Wakefield, Waltham, Wel- 
lesley, Weston, West Acton, West Newbury, Wilmington, Win- 
chester, Woburn. 

This list indicates the localities where the fungus has been 
planted, but not the number of plantings. In many instances 
several plantings were made in the same town. 



27 



List of Hosts of Entomophihora Aulicce Reich, reported in the United 
States. Hosts of Empusa grylli Fres. are excluded. 

Agrotis sp., cutworm, Thaxter. 1 

Catocala sp., Clinton. 

Estigmene acraea, salt-marsh caterpillar, . . . Clinton. 
Euproctis chrysorrhoea, brown-tail moth caterpillar, Kirkland, Stone 

and others. 2 
Hyphantria textor, fall webworm, . . . . Thaxter. 5 

Lithophane (Xylina), cutworm, Thaxter. 1 

Malacosoma americana, tent caterpillar, . . . Clinton. 
Mamestra sp., cutworm, ...... Thaxter. 1 

Orgyia nova, rusty tussock moth, .... Thaxter. 8 

Phlegethontius Carolina, tomato worm, . . . Thaxter. 1 
Phlegethontius celeus, tomato worm, .... Thaxter. 1 

Pyrrharctia isabella, Isabella moth, .... Thaxter. 8 

Spilosoma virginica, yellow bear, 



Thaxter. 8 
Webster/ 

Euehetes Egle, Thaxter, herb. 

Smerinthus modestus, ....... Thaxter, herb. 

Amphipyra pyramidoides, ...... Thaxter, herb. 

Larva of diurnal lepidoptera, probably Vanessa, . Thaxter, herb. 

Larva of diurnal lepidoptera, sp., .... Thaxter, herb. 

1 Ann. Rept. Connecticut Agri. Exp. Sta., 1890; 98, 1891. 

2 Ann. Rept. Mass. Supt. Suppression of Gypsy and Brown-tail Moths, 1, 130, 1936. 

3 Mem. Boston Soc. Nat. History, IV.; 159-162, 1888. 

* Journal Cincinnati Soc. Nat. History, XVI.; 175, 1894. 

EXPERIMENTS WITH THE GYPSY FUNGUS. 

In the spring of 1908, while Dr. Clinton was carrying on 
preliminary experiments "with the brown-tail fungus, he re- 
ceived from the Melrose laboratory specimens of Japanese 
gypsy larvse, shipped from Japan with other material, which 
had been killed by the attack of an Entomophihora, but owing 
to the fact that the caterpillars had been dead for some weeks, 
all attempts to make this fungus develop its spores were unsuc- 
cessful. As it was thought that this species of Entomophihora 
might be as effective in destroying the gypsy larvse as Ento- 
mophihora Aulicce was in destroying the brown-tail, Dr. Clin- 
ton, through the generosity of a friend of Harvard University, 
was sent to Japan to obtain the living fungus, and after great 
difficulties succeeded in bringing a few infected Japanese cater- 



28 ' 

pillars to Cambridge. Of the few larvae which survived the 
long trip and severe heat only two developed the disease. 
These two were put immediately into a moist culture dish, 
so arranged that the spores would be discharged on healthy 
caterpillars. Only one of the latter developed typical conidia, 
but the growth was so feeble that probably very few spores were 
discharged. The pustules of conidiophores and attached spores 
were picked off and transferred directly to healthy caterpillars, 
and the dead bodies of the few larvae which had developed rest- 
ing spores were carefully saved. The caterpillars directly inoc- 
ulated showed signs of the disease externally on the eighth day 
after infection, but in no case was the appearance typical. 
From this generation of the fungus 30 caterpillars were inoc- 
ulated directly as above, and by successive transfers the num- 
ber which developed the conidial form of the disease was 
increased steadily, though slowly. Resting spores were gen- 
erally formed with the conidia. By the time the disease was 
running well in the infection boxes the larvae in the field had 
practically all become prepupae or pupae, and since the attempt 
to raise caterpillars from cold-storage eggs was unsuccessful, the 
disease, from lack of hosts on which it could be propagated, 
died out late in August. 

Healthy gypsy larvae were put into the infection box of the 
previous spring on May 15, 1910, and the disease, which de- 
veloped spontaneously on the 2d of June, was kept running 
until the last of August. Reinfection was undoubtedly accom- 
plished through the germination of some of the thousands of 
resting spores, formed during the previous season, which were 
lying on the bottom of the box. From June 15 to July 2 six 
plantings were made, following the same methods used suc- 
cessfully with the brown-tail fungus, in Billerica. Brookline, 
Lynn, Saugus and North Wilmington, but regular and careful 
inspection of these plantings revealed neither the conidial nor 
the more common resting-spore stage of the fungus. 

In the spring of 1911 the same plantings were inspected 
carefully to see whether the disease had possibly started as a 
result of the infection made in 1910. but no indication of its 
presence was discovered. The disease boxes at the garden had 
not been disturbed during the winter, so thev contained all the 



PLATE VI. 




Gypsy caterpillars dead from a disease similar to the brown-tail fungus. Note the 
characteristic position of the body of the dead caterpillars. 



29 

resting spores formed in 1909 and 1910, except those which 
must have germinated and the few removed for experiment 
and examination. The disease appeared on the 23d of May, 
when a very small larva broke out with a few feebly growing 
pustules. On the 27th a half-grown caterpillar died from the 
disease in the greenhouse, and again on the 9th of June a large 
gypsy was found rigid and ready to shoot. From these larvse, 
and from others which subsequently developed the disease, 
about 500 caterpillars were directly inoculated, but it was not 
until the 19th of June that the supply of diseased material 
warranted the first planting, at Brookline. On the 24th and 
26th of June two other plantings were made in a badly infested 
scrub oak woodland in Roberts. Careful inspection on the 
29th of June, and on the 6th and 15th of July, failed to reveal 
the slightest sign of the fungus in either of these plantings. 
The wilt disease appeared to be universally distributed wher- 
ever the gypsies were feeding, and was severe enough during 
the hot weather of the last half of June and of early July to 
kill off the caterpillars in the rearing boxes and the disease 
boxes at the garden to such an extent that the propagation of 
the fungus became more and more difficult, until finally it had 
to be abandoned, owing to the total destruction of the culture 
larva?. 

Conclusions from work on the Gypsy Fungus. 

The experiments with the gypsy fungus, notwithstanding 
the fact that they were made under unfavorable weather condi- 
tions, both in 1910 and 1911, indicate that this disease is not 
a promising form for artificial use. This conclusion is based 
not only on the fact that the fungus is itself far more difficult 
to propagate than that of the brown-tail, and is much more sen- 
sitive to unfavorable weather conditions, but is also evident 
from the fact that the breeding in confinement of gypsy larva? 
is associated with difficulties which are in themselves sufficient 
to render the continuous propagation of the fungus from month 
to month or from year to year almost impossible. 

Should it obtain a foothold in the field, however, it might be 
expected to prove continuously effective from season to season, 
owing to its habit of forming resting spores in great abundance, 
which the experiments have shown are able to survive the New 



30 

England winter, and a very slight increase in virulence, such as 
often appears in parasitic fungi in successive seasons, might 
bring about quite different results from those above reported. 

LITERATURE. 

Among some of the more important articles dealing with 
insect diseases and their practical use the following may be 
mentioned : — 

1855. Cohx, F. Empusa muscce und die Krankheit der Stubenfliegen. 
Nova Acta Acad. Caes. Leop. Carol, d. Nat., XXV., 301, 
1855. 

1869. Reichardt. Empusa Aulica:. In Bail, Ueber Pilzepizootien in 
Schriften d. Natur. Ges. Danzig. N. F. Band II., 3, 1869. 

1875. Cojtnt, F. Entomophthora Aulicre. Beit. z. Biol. d. Pflanzen, 
Band I., Heft VII., 1875. 

1882. Nowakowski, L. EntonvopMTioracece. Report in Bot. Zeit., 
1882, 560. 

188S. Thaxter, R. The Entomophthorecc of the United States. Mem. 
Boston Soc. Nat. Hist., 4, 133-201, 1888. 
Forbes, S. A. On the Present State of our Knowledge concern- 
ing Contagious Insect Diseases. Psyche, Vol. V., 3, January- 
February, 1888. 

1889. Giard, A. Review of Krassiltschik's " De Insectorum Morbis 
qui Fungis Parasiticus Efficiuntur." Bui. Sci. de France et de 
la Belgique, Tome XX., 120-136, 1889. 
Snow, F. H. Experiments on Artificial Dissemination of Con- 
tagious Diseases among Chinch Bugs. Kansas Academy of 
Sciences, Vol. XII., Topeka, 1889. 

1892. Buisson, M. Le Botrytis tenella. Nouveau Moyen de detruire 

les Vers Blancs et les Hannetons. Compiegne, Imprimerie 
Henry Lefebvre, 31 Rue Solferino, 1892. 

1893. Giard, A. L'Isaria densa. Bui. Sci. de la France et de la Bel- 

gique, Tome XXIV., 1893. 
1895. Pettit, R. H. Studies in Artificial Cultures of Entomogenous 

Fungi. Bui. 97, Cornell University Agri. Exp. Sta., 1895. 
1S97. Rolfs, P. H. A Fungous Disease of the San Jose Scale, Sphce- 

rostilbe coccophila Tul., Bui. 41, Florida Agri. Exp. Sta., 1897. 
1901. Danysz, M. J., and Wize, M le Dr. K. De L'utilisation des 

Muscardine dans la Lutte avec le Cleonus punctiventris. 

Libraire Agricole de la Maison Rustique. 26 Rue Jacob, 

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31 

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Explanation of Plate VII. 

Figs. 1-4. — Typical conidia. 

Figs. 5-7. — Germinating conidia. 

Fig. 8. — Secondary conidium produced directly from a primary conidium. 

Fig. 9. — Four small hyphal bodies. 

Fig. 10. — Group of conidiophores showing four stages, a, b, c and d, in the development 
of the conidium. 

Fig. 11. — An abnormal hyphal body, apparently partially encysted. 

Figs. 12-17. — Characteristic forms of hyphal bodies prior to and during the formation 
of resting spores. 

Fig. 18. — A mature resting spore. 

Fig. 19. — Section through the body of a caterpillar, showing the relation of the conid- 
iophores to the integument. 



PLATE VII. 




Explanation of Plate VIII. 
FIGS. 20-21. — Encysted hyphal bodies (autumn). 
Figs. 22-23. — Germination of the encysted hyphal bodies. 
Fig. 24. — A conidiophore, showing the old walls of primary, secondary and tertiary 

conidia which have germinated iti situ. 
Fig. 25. — Pustule of conidiophores which developed from germinating encysted hyphal 

bodies in a culture dish in the laboratory. 
Fig. 26.— Section view of a similar pustule breaking through the integument. 
Fig. 27.— Formation of a conidium from the germination of an encysted hyphal body. 
Figs. 28-31. — Germination of the ordinary type of hyphal bodies. 
Fig. 32. — A germinating conidium showing the cross septa a which closes the empty tube 

after the advancing protoplasm. 
Fig. 33. — An abnormally large hyphal body. 

All the figures were drawn with the aid of the camera lucida, and are reduced about 
one third in reproduction. With the exception of Figs. 19, 25, 26 and 27 the magnification 
was approximately 425; for Fig. 19 the magnification was about 90; for Figs. 25 and 26, 
about 300 ; and for Fig. 27, about 600. 



PLATE VIII. 




